Glaucoma is one of the leading causes of blindness worldwide, yet many people are unaware they have it until significant damage has already occurred. Here we explain what glaucoma is, what causes it, its symptoms and how it can be treated.
What is glaucoma?
Glaucoma is a group of eye conditions that damage the optic nerve — the nerve that carries visual information from the eye to the brain. In most cases, this damage is caused by abnormally high pressure inside the eye (intraocular pressure).
Without treatment, glaucoma can cause permanent vision loss. It is the second leading cause of blindness in the world, after cataracts.
What causes glaucoma?
The eye continually produces a fluid called aqueous humour. This fluid normally drains out through a mesh-like channel. If this channel becomes blocked, or the eye produces too much fluid, pressure builds up inside the eye. This increased pressure can damage the optic nerve, leading to glaucoma.
In some cases, glaucoma can develop even when eye pressure is normal, which is known as normal-tension glaucoma.
Types of glaucoma
Open-angle glaucoma
The most common form of glaucoma, open-angle glaucoma develops slowly over time. The drainage angle formed by the cornea and iris remains open, but the drainage channels in the trabecular meshwork are partially blocked, causing pressure to gradually increase.
Acute angle-closure glaucoma
This type occurs when the iris bulges forward, narrowing or blocking the drainage angle. This can cause a sudden increase in eye pressure. Symptoms include severe headaches, eye pain, nausea, blurred vision and seeing halos around lights. This is a medical emergency requiring immediate treatment.
Normal-tension glaucoma
In this type, the optic nerve becomes damaged even though eye pressure is within the normal range. The exact cause is not fully understood, but poor blood supply to the optic nerve or particular sensitivity in the nerve may be contributing factors.
Secondary glaucoma
This type is caused by another eye condition or injury. Causes can include eye inflammation (uveitis), diabetes, advanced cataracts, or the use of certain medications such as steroids.
Glaucoma symptoms
The most common type — open-angle glaucoma — often has no symptoms in the early stages. Vision loss typically begins at the edges (peripheral vision) and progresses inward. By the time central vision is affected, significant damage has already occurred.
Symptoms to look out for include:
- Gradual loss of peripheral vision
- Tunnel vision in advanced stages
- Blurred vision
- Eye pain or pressure (more common in acute angle-closure glaucoma)
- Headaches
- Seeing halos around lights
- Redness of the eye
Risk factors for glaucoma
Anyone can develop glaucoma, but certain factors increase the risk:
- Age: The risk increases significantly after the age of 60
- Family history: Having a close relative with glaucoma increases your risk
- High eye pressure: Even if no damage is present, elevated intraocular pressure is a risk factor
- Medical conditions: Diabetes, high blood pressure and heart disease are associated with higher risk
- Eye conditions: Extreme short-sightedness (myopia) or long-sightedness (hyperopia), eye injuries, certain eye surgeries and thin corneas can all increase risk
- Prolonged use of corticosteroids: Especially eye drops
How is glaucoma diagnosed?
Regular eye examinations are essential for early detection. During a glaucoma check, your optician may:
- Measure your intraocular pressure (tonometry)
- Inspect your drainage angle (gonioscopy)
- Examine your optic nerve (ophthalmoscopy)
- Test your field of vision (perimetry)
- Measure the thickness of your cornea (pachymetry)
Glaucoma treatment
While glaucoma cannot be cured and any vision already lost cannot be restored, treatment can slow or prevent further damage.
Eye drops
The most common treatment for glaucoma is prescription eye drops, which either reduce the production of fluid in the eye or improve its drainage, or both. It is important to use them exactly as prescribed.
Oral medication
If eye drops alone are not effective, your doctor may prescribe oral medication (usually a carbonic anhydrase inhibitor) to reduce eye pressure.
Laser treatment
Laser therapy can help fluid drain from the eye more effectively. The most common laser treatments include selective laser trabeculoplasty (SLT) for open-angle glaucoma, and laser peripheral iridotomy (LPI) for angle-closure glaucoma.
Surgery
When medication and laser treatment are insufficient, surgery may be recommended. The most common procedure is trabeculectomy, which creates a new drainage channel. Other options include drainage implants.
Looking after your eye health
Early detection is key to managing glaucoma effectively. Regular eye tests — at least every two years, or more frequently if you are at higher risk — are the best way to catch glaucoma before it causes significant vision loss. If you are concerned about your eye health, speak to your optician.